Attached is a paper I have written of how a Block II configuration of SLS can be used to return humans to the Moon in a single launch. If you feel you are not proficient enough in mathematics, I suggest only reading the Introduction and Conclusion of the paper. The abstract is below.

"We examine how a 140 t to low Earth orbit (LEO) Block II configuration of the Space Launch System (SLS) can be used to perform a crewed Lunar landing in a single launch. We show that existing RSRMV solid rocket motors can be used to achieved Block II performance by using a core with six RS–25E engines and a large upper stage (LUS) with two J–2X engines. A cryogenic propulsion stage (CPS) with four RL–10C–2 engines is used to perform trans Lunar injection (TLI), Lunar orbit insertion (LOI) and 75% of powered descent to the Lunar surface. A Lunar module (LM) initially carrying two crew and 535 kg of cargo is used to perform the remaining 25% of Lunar descent. The LM is in two parts consisting of a crew and propulsion module (CPM) and non–propulsive landing and cargo module (LCM). The CPM returns the crew and 100 kg of samples to the waiting Orion in Lunar orbit for return to Earth."

Thanks Steven. This type of study is exactly why I'm at Nasaspaceflight. We're here because we're dreamers, not because we think something can't or won't happen. The more exercises like this that you and any of our other resident experts can do, the better for all of us, if only for the education into what is possible.

Well done. I intend to read it from front to back several times, and I will be much better informed as a result.

You assume SLS 1B with EUS can insert ~26t into LLO, approx. the same as Orion (I remember seeing numbers up to 30t (?) elsewhere..). Shouldn't a lander of such size be capable of delivering significantly more mass to the surface than your solution? For a quick sortie that may not matter, but if you want to build and resupply an outpost...

IMO 2 SLS 1B are only wasteful if you cannot utilize their performance entirely.

IMO 2 SLS 1B are only wasteful if you cannot utilize their performance entirely.

ISTM one of the issues with SLS is that the flight rate is critically low to keep the ground crews fighting fit.

At some point it makes sense to stop spending money on development, and instead spend it on building rockets and flying missions. Which I think is the point of block 1B.

Downside is that two widely spaced launches with LEO rendezvous has major boiloff issues. LOR and a lander with storable prop seems to me to be the method which requires the least development money to implement.

First off this paper is a tribute to the 46th anniversary of the Apollo Lunar landing. This paper shows there is still interest in crew missions to the Earth moon. I believe it best if commercial were to take over from here and NASA buy rides to the moon for it's science missions.

1 ) Added cost to develop when the U.S. needs the funds for another launch vehicle for national needs.

2 ) Low flight rate ( brain drain )

3 ) Missions would be going on in early 2030's when nation was to be heading to Mars ( crew missions )

However it could have two launchs a year. One cargo and the other crew.

11 launches, first a test flight and the other 10 missions to Lunar surface.

Cargo landings could be a Hab with wheels. Could travel to another site by Earth remote control between missions. Another cargo landings could bring rover, science equipment, added food water for extended stay, ect.

While I somewhat agree that NASA should try to avoid "building" rockets, what commercial options do they have for the payload mass they're talking about? Should they wait for SpaceX's BFR? What happens if it doesn't come to fruition, and if it does, what kind of political fallout would ensue in the event that it's a failure? Besides that, they have no other options.

While I do think the SLS is unwarranted for the time being as it doesn't even have any definitive missions, nevermind the extreme cost, I do understand why NASA wants to design a rocket to their spec (and of course you have some in congress demanding it). Sure, they could pour that money in expediting BFR development, but there would be [somewhat understandable] cries coming from all corners of aerospace and government regarding such subsidies of one company, and I doubt SpaceX would want to share development with anyone else on that project.

While I somewhat agree that NASA should try to avoid "building" rockets, what commercial options do they have for the payload mass they're talking about? Should they wait for SpaceX's BFR? What happens if it doesn't come to fruition, and if it does, what kind of political fallout would ensue in the event that it's a failure? Besides that, they have no other options.

While I do think the SLS is unwarranted for the time being as it doesn't even have any definitive missions, nevermind the extreme cost, I do understand why NASA wants to design a rocket to their spec (and of course you have some in congress demanding it). Sure, they could pour that money in expediting BFR development, but there would be [somewhat understandable] cries coming from all corners of aerospace and government regarding such subsidies of one company, and I doubt SpaceX would want to share development with anyone else on that project.

For Lunar missions I was referring to Vulcan/ACES ( cost to develop SLS block II from the paper could fund Vulcan/ACES ). There is no commercial option that I know of ( including BFR as we have no public specs or know if it has full funding ).

SLS can only launch one at a time. It would still need to place payload in LEO if it were to send two crew creaft to Lunar orbit for safety ( from t/Space concept ). Yes they can use the lander as a life boat, but if Orion is damaged to badly for Earth reentry then crew could be lost. Vulcan/ACES offers the two craft option with much higher flight rates. All parts are light enough that a Vulcan can take it to LEO staging point. If we invested in Vulcan/ACES it is for other than crew BLEO exploration , that is a bonus. We don't know if we will see funding for missions to Lunar or other BLEO missions. So Vulcan/ACES can do the job if needed and there is funding, it is designed to handle the needed launches, unlike SLS block I/II.

Steven did a good job with his paper and use of SLS block II for a single Lunar launch mission. However we are ready for the next steps for BLEO crew misions. That will take commercial to see Lunar return. Unless there is a payload that Vulcan or Falcon heavy can't handle I don't see this happening, just to much money to repeat Apollo with a little longer stays. Plus SLS could only launch twice a year and that would use up all SLS flight for five plus years for the eleven missions just for Lunar.

So what do you think of the Lunar missions in the paper and what do you like ( lander, ascender ect. )?

Shouldn't a lander of such size be capable of delivering significantly more mass to the surface than your solution? For a quick sortie that may not matter, but if you want to build and resupply an outpost...

I haven't crunched the numbers, but I would expect a dual Block IB mission to be able to land more cargo. Afterall, you are putting 186 t into LEO compared to 140 t.

Downside is that two widely spaced launches with LEO rendezvous has major boiloff issues. LOR and a lander with storable prop seems to me to be the method which requires the least development money to implement.

That's right. In a dual Block IB mission, the Lunar lander using storable propellants would be sent first to wait in LLO for Orion, so there are no boiloff issues.

Logged

Akin's Laws of Spacecraft Design #1: Engineering is done with numbers. Analysis without numbers is only an opinion.

...SLS could only launch twice a year and that would use up all SLS flight for five plus years for the eleven missions just for Lunar.

Just a slight clarification -- they can only, at this time, make two SLS boosters a year. If several are made up in advance, the latest thinking is that they could be launched every 120 days in "salvo" mode, meaning with present construction and launch flow capability, they could launch three a year. And if a program was funded that required a higher flight rate, assuming you could make enough of them, you could increase that flight rate to up to five or six launches a year, based on the capability proven during Apollo to be able to launch every 60 days off of one pad. (Yes, they did ease their constraints somewhat by launching Apollo 10 from 39B, but could easily have kept to the same launch schedule and only used 39A if they had chosen to do so.)

...SLS could only launch twice a year and that would use up all SLS flight for five plus years for the eleven missions just for Lunar.

Just a slight clarification -- they can only, at this time, make two SLS boosters a year. If several are made up in advance, the latest thinking is that they could be launched every 120 days in "salvo" mode, meaning with present construction and launch flow capability, they could launch three a year. And if a program was funded that required a higher flight rate, assuming you could make enough of them, you could increase that flight rate to up to five or six launches a year, based on the capability proven during Apollo to be able to launch every 60 days off of one pad. (Yes, they did ease their constraints somewhat by launching Apollo 10 from 39B, but could easily have kept to the same launch schedule and only used 39A if they had chosen to do so.)

More than three a year, very unlikely! But three launches is needed to help the brain drain.

What are the goals for these 11 crew landings?

The goals could be done by teleoperated rovers. Samples could be sent back if wanted by a t/Space like capsule. Atlas V and or Falcon heavy ( might need two launches, one EDS the other lander ) could send these landers to the Lunar surface. Just the development cost for SLS block II would pay for the launches, landers and some of the mission cost. The launch and missions cost if using SLS block II would pay for Vulcan/ACES development. So for the total investment of SLS block II and the 11 missions we could have 10 to 11 robotic Lunar missions plus Vulcan/ACES development. Robotic can cover more ground. So what is the better invetment? Crew can be sent latter if wanted. And ULA's 2009 paper on ACES for Lunar also has opening plans for ACES Mars.

With robotic missions not loss of crew risk. If the is a LOM it is not a big deal and we can move on without a big deal. Using existing commercial launch vehicles we would not be commited to 6 to 11 missions with a big development cost to justify. By the time the first 6 robotic missions could be launched ACES/Orion could be ready to send crew. We need to build our needed infrastructure to handle(modern crew BLEO missions ( not Apollo demonstration we can do it mission of the 1960's ). We need to have the ability to routinely send crew BLEO, not just once in a while. If Saturn Apollo program had continued it would have needed to evolve, lower cost , less risk, fast launch rates for crew and cargo.

I had some fun making the rocket described in KSP with Realism Overhaul installed, since this looks like a quick and fun mission to try out. I made a baseline 5seg SRB + six SSME core + 2 J2-X LUS configuration using the tank sizes outlined in your pdf.

On my first try, I got a 157 ton payload consisting of an almost full EUS (~150 m/s circularization delta-v used) and some lead ballast to a 233 x 290 km orbit at 28.68 degrees inclination. Looks like there's quite a lot of margin in the design. One thing which may have increased the payload is a slightly higher thrust profile on the SRB's with a 95 second burnout time rather than 128 seconds. This may have reduced gravity losses and increased payload. The FAR atmosphere model in the modpack is great but may have underestimated the drag losses.

I'll enact the full mission in KSP and post a video of it on youtube in a few days.

For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v. Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Shouldn't a lander of such size be capable of delivering significantly more mass to the surface than your solution? For a quick sortie that may not matter, but if you want to build and resupply an outpost...

I haven't crunched the numbers, but I would expect a dual Block IB mission to be able to land more cargo. Afterall, you are putting 186 t into LEO compared to 140 t.

Dual block 1B (RSRMV + EUS with RL10C) would be 210-225t to LEO, and ~80t through TLI.

Shouldn't a lander of such size be capable of delivering significantly more mass to the surface than your solution? For a quick sortie that may not matter, but if you want to build and resupply an outpost...

I haven't crunched the numbers, but I would expect a dual Block IB mission to be able to land more cargo. Afterall, you are putting 186 t into LEO compared to 140 t.

Dual block 1B (RSRMV + EUS with RL10C) would be 210-225t to LEO, and ~80t through TLI.

Not including the EUS, payload is 39 t. Including the EUS, payload is 51 t.

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So could it get Orion into LLO?

Yes, no problem.

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Could it get Steven's Lunar lander to Lunar surface? If so then could get rovers ( probe ) before crew landings and test out the lander.

You would use a large Apollo type lander using storable propellants. Rovers and payloads would be stored in the triangular payload compartments in the descent stage.

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On descent to Lunar surface were is the CPS attached to the Lunar lander ( top or bottom )?

You can't use the EUS, as the Lander would be waiting for several months in LLO for Orion to arrive. All its propellant would boiloff.

So SLS block IB could get an Apollo style LEM on the Lunar surface with about 50% increase in payload mass ( cargo ) or a 3 crew ascender?

A hypergolic fueled lander can wait in LLO for Orion/Crew. No CPS for descent needed.

For your SLS block II were is your lander attached to the CPS on descent to Lunar surface ( on the landers bottom or top?

So why develop block II if not needed for Lunar? Block IB could deliver great payload mass to the Lunar surface and more crew. For cargo only block IB is better sized. For the same amount of missions development and launch cost would be about the same. If a larger HLV is needed for Mars or other in the future then we could develop what is needed then.